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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '908487aa3914a47ee5a313429067f31a5ead94d72f7b6248fa951f2ff4d5ab77' 
  AND token = 'y4beN9E1I75UVIsmYcpPAnt5bH5pVQphdmrWLgRR18k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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