SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a87316092f8fa346ec1de71446cafb5598d1e881a482fec76491a2929a035e' 
  AND token = 'BllVhDmeDTUe5u+6q/5yFgpeN3tJgI62jyhy0/bJwzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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