SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c29b9dd48daf99e067ef58359abb70da98978291965bb8740a0e78684c1bd903' 
  AND token = 'SpVZh9zBcazi9w6+mXjxsS2QGpop4GrwSpt6hrzJYvM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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