SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68377cf3cc8f13e858c25e558b5d71545b276719778b1f099deef4eba42bd942' 
  AND token = 'dQL1Ksa24gEPwsmZjwmP+A2ThnyWS++VsWGe9lIGJnA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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