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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7d4eb9984c91618fcd3981944644fa4315433e516942a9d7fd08b5821bc78f87' 
  AND token = '3zJfHtgeaE3YssTIQobbWu20lUjtR+R3p8tH1n1Mujg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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