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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd21be30ff0378e7b8f6b2e08ce866ef3d5429515547675cb19ad9cf919a52633' 
  AND token = '8oDHF0CFQTIa+tmvZE6fiFA9rwZbM/p9aBC3ZilAMOw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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