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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6a70f3d47c80c144d5250bfd56b4d44b7000bf9e0172b63a4b8c1a1d46d4b71' 
  AND token = 'jnm0z+9pPLJIfGpONUP/0xw1b2EOxNaOYZQLda4EsO4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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