SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '261674d029832ca413dc89ccaabc45d4f383e559de3375c84478b6b4090f6ef4' 
  AND token = 'RimxKUql+t9u6COV/AUgheRfVJve0VBqHUdjvS/pwYQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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