SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff16f79aead62cfc13937539767db13f9735fd604e25312999a8ded9535e1055' 
  AND token = 'YKBp9P36XeFfuzvSHEOhV6XTLvC2iGqZLFQ2U3bX1wA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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