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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21682ff7e464a854f61419dd69d7089f33d2c5e2c48b812f39f9f14a2ee31c60' 
  AND token = 'xkDUG052GYf4sjOyCI8x8m7SfD5vz5DG2uRqM+Gk/LY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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