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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5398a3b7f7e252e3ea67a37bbafbfe7d70f84e3a4c20b60ad4c1bab58578a0f4' 
  AND token = 'y3lO1Zid6QqlCRTzLfCPgE/xlhVti39c6A1Hh+wN+vo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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