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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d15600b91ea55605b5993c8e0ebe495e956bf10ac447ef4f48c687e80e4fd19' 
  AND token = '1mZflfwXi//61ityYwrGp2RZXzU/0hVL4JqrPlWVoQY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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