SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8f5995382f5c57761a0f6eeb21d9c2994aa57842775becb426175bb76ae42dc' 
  AND token = 'll8zMHiD1VqsdT4V/V5xvhYhzowAWdPYEIi5VxTFg+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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