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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b79cc3f1a61ad8c9289b3288a48814a84bd953993e833c915b3c86c493b1af97' 
  AND token = 'OQ4syMC2k0hBDnYwElc0Rw4VFA7sOnMUrRqIF+HgBrg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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