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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '977150be278790cad16805e3cb7ff91be4673604ddeb316c430fd21ec480def5' 
  AND token = 'mqlocalcjweOE9hSv9PCSzcTr4dtSV3hIi25F0cgatU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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