SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '77916e63a31701d78160bc52892aed55197aededb947b6a949506d5138b79c5c' 
  AND token = '/rBrMcKiTvkXBMBXyG6M2/M/foZVrWfmns4u2mTP9Rk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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