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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c4036ba42a99c3ea2d67bc2ff4773d7d0ca29e27c98d727264bab984c0578f58' 
  AND token = 'JOMycFu8GzWWRmaQpKItEcfhMAzsNY6GDqauCF0hDuo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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