SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '876838fc428dae095e877bd5f50bc5e581a6c534eff5421021c042ef38dc9bb8' 
  AND token = 'umLUHBBi4XJmjlq/N4vqg9zDfn4VdehrhQ7SQKqvTj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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