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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '312a39170601a629bac283ce1b16758bc64962367abb5f451b94a1796d70a1e4' 
  AND token = '0Gn+3PWwOExTYEkcg8g0FtakOE1iunUbx7tHkZ61Ibg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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