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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b576e45b7f1e28f0ff0794f151d356ee7f99e08044de581139e2598ad52d5454' 
  AND token = '53djSiTytVNzaZz+CxhlUNt31+nu0A2re+dM3+z7wds=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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