SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'b71f21a78ddd54e552649875996456b61d7b74fc1937c58d815cce364fdd7308' 
  AND token = 'HPa/ZAuh3+IsVjDPjKDUrBTd9g3cSUqVReIXzvuvyX4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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