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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '876dcfc76e8fce5d44955cab067ae8ac1f9d5caaa2470ede95ad3dffced1dde5' 
  AND token = 'uiReATot6OV1JaAadLSkZ12RzxDyWhNv+7HEXt7aShY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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