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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a75f34e5995c7cfab6505d4a95bf7df8377315183d0e2ae253e6c2fa659d07f2' 
  AND token = 'OB9j+vrwrtEDekMiYFbK6+2Y/nSyF7yvOVmwUoK4rPE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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