SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff6c1b23b52e6330f06b579ee8382b2c19054d9c2e9cacfdb8858c7f2d7ebe3a' 
  AND token = 'oUD4sKYCd4aMgj7hBGF1DKYZTl583QW56qGg3RisRhM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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