SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a756df4ceda21dcd8fafd759f58be40affedc4fed883008384be6078293dd541' 
  AND token = '+25l6+AitZTP7br3gff+rJZeGAv2kjFXjedo23avWx0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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