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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '76b0e5c29ef3ee0a1a87a99e5bba781f3b7241600c176079eefb73316411a426' 
  AND token = 'PIsVzp5bSur1oNtSEr89EJvBq2UbeMhBud668BnepHs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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