SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '817f458e0d099837d1d0e85f9d64552e565941228bea27b6d882a96087940dc8' 
  AND token = 'eEJ5Nk8Gw2q8teG7yyrFvfr00USfFIF71cwuRnPlATE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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