SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51ca3b59a1fdfb93a0fff977b5ebffd7acd8a0658b1bfbea25d9dbecb097272' 
  AND token = 'vGSLnOM6V/lnWBJmOjpZGnKOPBamBPdvp13nukmphLc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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