SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c9b2e59fd19832c1117bb60e2858694000cea43e338ee87e1ca8df55218b47d' 
  AND token = 'IARZplcdQfh5agrDBNVP6hSEjCZxgKmg/htioZBXBds=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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