SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5138540bb704749b77604a58aac3792fb84d0480377e11f89bdabc108ee6b792' 
  AND token = 'hiXCCGwgKZvFZteFOHSxGWj++7DgjqV1w8FueMrh63s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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