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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b3dfe7a515cb319e41265bc49e03aabbb3e61af4500a840b60706a659645af38' 
  AND token = '6sFyNCV2tlngEgyoLiJNiCEW/V5HpbYByK0iofwFpxY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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