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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7fe2c832e923ed9de9e5bd0c960e017fc91dea3cd793eecd91ea5aa815aeda9' 
  AND token = 'KmtxGK0OXhBwFBphwoyP7HjLUS45rA+mNr/sWGuKSU0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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