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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af5ea73a51ecf4e5d3e2d82c9e68c66ee83535c887b767c81fbaec4d447ed1b3' 
  AND token = 'Dnbz1C65lczv8/AqmhuSVhAWd+VAxvoPPC/gUYepr0Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}