SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b249215a42a98bd0fe03b3e478c717fa4abf26fe79bdb9a25e954fb7753899c3' 
  AND token = '+AFIzCaiWrjkXBlkmOcmIs7O2vgR8MkCx3as/Zfk6IQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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