SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '88be1f2d6619019babcd048902079970a380931259be77691bc9c4e7aba477c7' 
  AND token = '+xcXRj6PHTB8pwHsyMrN3k0MjGL6DWJfiiS+lLoLlY0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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