SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ec43666cd85e22c5b27a17151a25e544c779e1dfe57d2749e4efdd0bda51784' 
  AND token = 'pSDMqrLEpYcsZV+51jyPKU3cTPRTIWAWOV/CsDsck+E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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