SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f97c31ba2a80ccd721787a34ffa1739a34b5cf6bce96bb4e180b604a552af5a6' 
  AND token = 'uuuQlYPMBmzhz7n/KXrEmZOnj2Z8nah5KUOaJ1Z/b3o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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