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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9cf52e315662bfb03b2387f8f02c900489c0a9c01690c06c228e7d2e48e803a' 
  AND token = 'JBtMisOdRl6nzo5UwvjwTBJ3mf0MYSR1mShwlrRQ/nY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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