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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e2dcf4a39ee0a5e23c3397fe45652219f26d36238c1cf18da03b80a504c5e4b0' 
  AND token = 'K4hjs6DY26D1LAhPBWrvwML3+uZBYmsWA6ZMzeDqrxQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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