SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '51b1a197c609a613d7114e53fd652a7e35001f2a1566e1e90a07870137f54d02' 
  AND token = 'JIAx8yVVVl/OdW+U5jkcWBt+GtdlFHfL7bMshb3wCnY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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