SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c51a77aec9e14175de1c5ded38825dd7e94ce4dbba5fe3d05883911a1b1617f' 
  AND token = 'iac5092eCfW97qkFauYSiA1bbnhUnJihDWUhKY2UBWk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}