SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '92b4b9a3f16a538cdf802052103a56aeec0eec7d26fb75de352cda5eb5ee5def' 
  AND token = 'elPk5T5HK45TI4bjSiOpA75InLLbiHBmHW5P6Jt109I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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