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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3751ada4d63c5d10707e3b4d4e2b946c089da3da5cabc7c9cb7e7b68af6a9027' 
  AND token = '6AU2yCwfElI4OvOnCNnuEWhu9POOxRUt/FtBv+uDFAE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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