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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cef3e9f9f4f9fef7ef162bbfd34bd6abe1a2512fdd44d66a113bc76e713e1f4c' 
  AND token = '5prMhEHVjuKmsUE4oJaNTZFt2TDSFnLNH9YBy9vimDk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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