SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bd78fdc1a2d2284ef4346118fe928500905bb1b78325122a0cb0d002b59cbbff' 
  AND token = 'T5e90cuRwvijnTALTGZlBBstyMdwkX2tIO3EnPm+xC4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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