SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3b62a138ed0457ae381def9709246379f5061e236db5883b41699e437c35a9b' 
  AND token = 'K70sNxprgriJ7nOROPONI5LEy628jfqbEbop2sPaStQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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