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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '140503ebfa34ae763f0cde4bd1b3977cdc313cfd1a6012fc18a9b1b16676ec2e' 
  AND token = 'bwqJ5Vd9WaWZ4+Zsgcmw2s7UECon4v88FqgYkr+jeRg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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