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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'de7fb79caa6e6142b3fde56b0a299b578775357af5103d6492a77f55f5cb3f3d' 
  AND token = 'qRqrkiEqEL7JcXOrF9+3eaYhVp4JVwqeVgDSL7dku5Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}