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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f31c68f4c85f95bb267070a041bfba77fe5d0c7728126d38182a5087ae735d4e' 
  AND token = 'SOscXS2gsJcPlcMnS3VoIAPGjQ8AtuDPvmYU5igfdzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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