SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb8046754ecbfe832e9e8aa043a77d18e534963a3b9a6596439f502dca772af7' 
  AND token = '68OMFC32840FMN1xtMsua5CDCu81CNplmFm8ueZMKBY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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