SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c1d99a806d79adc74b5b230a3b081ce6d6ade9da321f2ada6c799362b979608' 
  AND token = 'SSsiEI2+vwCRKoluUTzeUkfNohFZXNff791LTPamXkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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