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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a15dc3d06151403fa57cc7fe427fcbfc7fedc963d2a3d0311b2f4ce2d95cf95f' 
  AND token = '9D96YdAc0SKmhaxPILikBrBiWf8LnAU4MHj8Ntu4tlE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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