SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb83a1cb1b02606c86fb8d3989e9da251e175158e47855acd44741320d5b580e' 
  AND token = 'R4m9FFFBjPztp8DcnVNG5FdICmYjFgFv1CpXusg/Z2Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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