SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe8715c35ae430f32c3c5652e92527e426c99e4c9d5215be40f5fbb39021eab5' 
  AND token = 'uSm7ThehmlkpMk63nyMLTJFkQFIG8Yta5Aoq0kMn9Lg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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